<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>02_变量与常量</title>
</head>
<body>
<script>
    var a = 1 ;
    console.log(a);
    var a = 2;
    console.log(a);
    var a = 2 ;
    console.log(a);
    var a = 3 ;
    console.log(a);
    var a = 3 ;
    console.log(a);

    let x = 1;
    console.log(x);

</script>
</body>
</html>